1. Field of the Invention
The present invention generally relates to a semiconductor device production method and a semiconductor device production apparatus, and more particularly, to a semiconductor device production method and a semiconductor device production apparatus in which grinding is performed on a wafer stuck to a tape.
In producing a semiconductor device, grinding is performed on the surface of the wafer so as to reduce the thickness of the wafer. However, a large load is applied to the wafer in the grinding step. For this reason, it has been desired that the grinding be performed at a high throughput without damaging the wafer.
2. Description of the Related Art
FIGS. 1 to 6 show a conventional semiconductor device production method and a conventional semiconductor production apparatus. It is widely known that a conventional semiconductor device production method includes a grinding step of grinding the rear surface of the wafer so as to thin the wafer to a desired thickness, and a dicing step of dicing the wafer into individual semiconductor chips.
Conventionally, there are two ways of performing the dicing step and the grinding step: as shown in FIG. 1A, the dicing step (step 10) is followed by the grinding step (step 11); or, as shown in FIG. 1B, the grinding step (step 20) is followed by the dicing step (step 21).
FIGS. 2 and 3 illustrate the dicing step (step 10) and the grinding step (step 11) of FIG. 1A.
A wafer 10 to be diced is fixed to a wafer frame 12 provided with a dicing tape 13. The dicing tape 13 is a resin tape coated with a ultraviolet curing adhesive, and the wafer 10 stuck to the dicing tape 13 is diced. The circuit forming surface (to which the dicing tape 13 is stuck) of the wafer 10 is covered with a protection tape 14 which protects the circuits in the wafer 10 at the time of dicing.
The wafer 10 is diced by a dicing saw 15, and is divided into individual semiconductor chips 11. At this point, groove-like gaps 16 each having a width corresponding to the blade width of the dicing saw 15 are formed between the semiconductor chips 11. The wafer 10 (i.e., the individual semiconductor chips 11) remains attached to the dicing tape 13 via the protection tape 14.
FIG. 3 illustrates the grinding step (step 11) carried out after the dicing step (step 10). In the grinding-step, a grinder 17 grinds the rear surface of the wafer 10 to thin the wafer 10 to a desired thickness. More specifically, the rotating grinder 17 supplied with an abrasive liquid is moved in the directions of arrows X1 and X2 shown in FIG. 3. Thus, the semiconductor chips 11 having the predetermined thickness can be formed.
FIG. 5 illustrates the grinding step (step 20) shown in FIG. 1B. In FIG. 5, the same components as in FIGS. 2 and 3 are indicated by the same reference numerals as well.
In the production method shown in FIG. 1B, the grinder 17 grinds the wafer 10 without the gaps 16, because the grinding step (step 20) is carried out prior to the dicing step (step 21). After the wafer 10 is thinned to the predetermined thickness by the grinding, the dicing step is carried out by the dicing saw 15 to form the semiconductor chips 11.
In the production method shown in FIG. 1A, the wafer 10 with the gaps 16 is ground, because the dicing step is carried out prior to the grinding step. The width W1 of each of the gaps 16 is substantially equal to the blade width of the dicing saw 15. More specifically, the width W1 is as small as about 20 xcexcm, for instance.
The wafer 10 is diced into the individual semiconductor chips 11, and the bottom of each of the semiconductor chips 11 is stuck to the dicing tape 13 via the protection tape 14. Because of this, the fixing force for each of the semiconductor chips 11 is small, often resulting in displacement. Also, since the grinder 17 moves in the directions of the arrows X1 and X2 while rotating, a large external force is applied to each of the semiconductor chips 11.
For the above reasons, the semiconductor chips 11 are displaced at the time of grinding, and collisions occur between the semiconductor chips 11. FIG. 4 shows the problem caused when the grinder 17 is moving in the direction of the arrow X1. The semiconductor chip 11 on the right side in the figure is subjected to the force (external force) in the X1 direction along with the movement of the grinder 17.
The semiconductor chip 11 subjected to the external force is displaced in the direction of an arrow A in the figure, and the upper corner of the semiconductor chip 11 collides with the adjacent semiconductor chip 11. The displaced position of the semiconductor chip 11 on the right side is indicated by a broken line. Because of the collision, a crack 18 might occur in the upper corner of the semiconductor chip 11, resulting in a poor production yield and a low throughput.
On the other hand, in the production method shown in FIG. 1B, the grinder 17 grinds the wafer 10 without the gaps 16 (as shown in FIG. 5), because the grinding step is carried out prior to the dicing step. Thus, the crack 18 shown in FIG. 4 can be prevented.
By the method of FIG. 1B, however, a warp is caused in the wafer 10 as shown in FIG. 10, when the wafer 10 is ground to the predetermined thickness. Such a warp can be measured by the maximum distance (indicated by an arrow H in the figure) between the dicing tape 13 (or the protection tape 14) and the wafer 10. If a 6-inch wafer is ground to a thickness of 200 xcexcm, a warp of about 2 cm is caused (H=2 cm). If an 8-inch wafer is ground to a thickness of 200 xcexcm, a warp of about 3 cm is caused (H=3 cm).
With such a warp in the wafer 10, it is difficult to handle the wafer 10 without damaging it. The possibility of the 8-inch wafer being broken is about 50%, resulting in a poor production yield and a lower throughput.
A general object of the present invention is to provide a semiconductor device production method and a semiconductor device production apparatus in which the above disadvantages are eliminated.
A more specific object of the present invention is to provide a semiconductor device production method and a semiconductor device production apparatus having a large yield and a high throughput.
The above objects of the present invention are achieved by a semiconductor device production method which includes the steps of: sticking a wafer to a tape stretchable by a physical process; dicing the wafer into individual semiconductor chips; stretching the tape by carrying out the physical process after the dicing; and grinding the rear surface of the wafer stuck to the tape after the tape stretching.
The above objects of the present invention are also achieved by another semiconductor device production method which includes the steps of: dicing a wafer whose rear surface is stuck to a dicing tape, the rear surface is opposite to the circuit forming surface of the wafer; sticking a tape onto the circuit forming surface of the wafer after the dicing, and removing the dicing tape from the rear surface of the wafer; stretching the tape by performing the physical process on the tape; and grinding the rear surface of the wafer stuck to the tape after the step of tape stretching.
The above objects of the present invention are also achieved by a semiconductor device production apparatus including: a dicing unit which dices a wafer stuck to a tape stretchable by a physical process; a physical process unit which stretches the tape by performing the physical process on the tape by physical process means; and a grinding unit which grinds a rear surface of the wafer by a grinder, with the tape being stuck to the wafer.
In the semiconductor device production method and apparatus of the present invention, the tape is stretched so that the gaps between the semiconductor chips become wider. With the wider gaps, even if displacement occurs in the semiconductor chips, the semiconductor chips do not collide with each other, and no crack is caused in the semiconductor chips. Thus, semiconductor devices can be produced at a high rate of yield and a high throughput.